Starter for engines



S. W. RUSHMORE.

STARTER FOR ENGINES.

APPLICATION FILED DEC. 20, 1919.

1,405,742 Patented Feb.7, 1922.

2 SHEET$-SHEET 1. 0 J

[HHHIIIHIIIHIIIIHXAIIWI F: G E E L J l S. W. RUSHMORE.

STARTER FOR ENGINES.

APPLICATION FILED 02020.1919.

1 ,405,742, Patented Feb. 7, 1922.

2 SHEETS-SHEET 2.

/ INl/E/VTOR HIS A TTORNE Y UNITED STATES PATENT OFF-ICE.

SAMUEL'W. RUSHMORE, 01" PLAINFIELD, NEW JERSEY.

STARTER FOR ENGINES.

Application filed December 20, 1919. Serial in. 346,481.

and State of New Jersey, have invented certain new and usefulImprovements in Starters for Engines, of which the following is aspecification.

My present invention relates to devices of the above type in which amotor driven pinion is shifted into driving engagement with a gear forrotating the crank shaft of the engine upon starting, and out ofengagement after starting. It relates more particularly to devices ofthe above type in which the pinion is shifted by screwing endwise alonga screw element on the driving member, when one rotates faster than theother. Such differential rotation is due to inertia effects upon suddenstarting or stopping, either of the motor or the engine, and someauxiliar device such as an eccentric weight or friction drag is commonlyemployed to retard rotation of the pinion.

In starting devices of the above type employed on automobiles, the powerfor starting is commonly afforded by an electric motor operating oncurrent derived from'the storage battery. Such motors accelerate withextreme rapidity the instant the circuit is closed. Consequently, theendwise screwing of the pinion either into or out of engagement with theengine gear is extremely rapid and the shock upon locking of the gear torotate with its shaft and the simultaneous taking up of the load is veryreat. A torque s ring may be employed or moderating sue shocks as setforth in another application of even date herewith.

Such spring when secured to a driving member at one end and to a drivenmember'at the other end permits the driven member to lag behind thedriver and thus yieldingly applles' the powerso as to moderate theshocks. n I

Such torque springs, however, are noisy and frequently break and oneobject of my presentinvention is to secure similar results without theuse of the torgue spring.

M present invention contemplates the emp oyment in this connection offriction driving means normally acting to appl to the pinion the maximumtorque require for starting the engine but so arranged as to afford acertain amount of slip at the in- Specification of Letters Patent.

Patented Feb. '7, 1922..

stant of excessive shock due to locking of the pinion and simultaneoustaking up of theload, when it contacts with the stop which limits itsendwise screwing movement.

An additional feature of my invention is organizing the parts in such away that the dl'lVlIlg plnlon itself will function mechanically throughsuitably related machine elements to automatically effect a slightrelease of the otherwise normally constant pressure of the frictioncoqipling, thereby permitting slip between the bers at the instant ofabnormal power manifestation due to the momentum of the spinning shaftand armature. Preferably this mechanism is so organized that after suchmomentary release the full normal pressure on the friction members isautomatically restored so that the full power normally available in themotor will be applied for driving the engine at the speed re uired forstarting.

The above and other eatures of my invention may be more fully understoodfrom the following descriptionin connection with the accompanyingdrawings, in which- Figure 1 is a schematic view partly in sectionshowing the organization of parts according to one desirable embodimentof my invention; and

. Figure 2' is a detailed view on a'somewhat larger scale showing amodification.

In these drawings the crank shaft C of the internal combustion engine isprovided with fly-wheel F having gear G formed'on the peripherythereof.In operative relation thereto are the electric starting motor 1,havingan armature shaft 2 carrying a screwthreaded sleeve 3, carrying aninternall threaded pinion 4 provided with gear teeth 5. The motor shaftis parallel with the crank shaft so that screwing of the pinion endwisealong the sleeve sets it into and out of mesh with the gear teeth on thefly wheel. Inward movement of the pinion is limited by a collar 6preferably integral with the armature "shaft 2. Any desired means may beemployed for retarding rotation of the pinion when the starting of theengine operates to drive the pinion faster than the motor shaft, as, forinstance, the friction spring 8.

Any suitable means may be employed for closingthe circuit of the motoras for in stance, the switch S connected in series with battery B.

The means for frictions-11y applying the riving and driven memdesiredtorque from the drive shaft 2 to the sleeve consist of the friction disc9 integral with sleeve 3 and the cooperating annulus 10 carried by thebox like structure 11 which is rigidly secured to the shaft 2 throughbolts 12 and disc 13 which is secured to the shaft 2 by set screw 14.

The friction disc 9 is forced into frictional engagement with theannulus 10 by means of spring 15. The area of the frictional surface andthe stiffness of spring 15 are predetermined with a view to transmittingfrom shaft 2 to pinion 4 the maximum torque required for rotating gearwheel G up to the starting speed.

It will be noted that spring 15 is not secured either to the driving ordriven memb(r and serves none of the functions of a torque spring; alsothe sleeve 3 is secured to the shaftonly by pressure of said spring 15forcing disc 9 into contact with annulus 10, Hence, said sleeve can beshifted endwise to the left to relieve the friction if sufiicient powerbe applied to compress the spring 15. Moreover, said sleeve may slip androtate at slower speed or even remain stationary while shaft 2 isrotating whenever. suflicient power is applied to overcome the normalfriction or when said friction is reduced or eliminated by the abovedescribed endwise movement of the sleeve to the left in opposition tothe pressure of spring 15.

From the above descri tion of the parts the operation of the device willbe readily understood. When the switch S is closed the armature shaft 2with its integral collar 6 and carrying with it the sleeve 3 will berotated. Rotation .of the pinion 4 will be revented or at least retardedby inertia. ence the pinion will screw endwise into mesh with gear G.The starting speed of the motor being very great. and practicallyunimpeded up to the moment when the gear 4 butts against collar 6 andthe pinion 4 being then practically stationary and in mesh wthstationary fiy-wheel gear G, there is an instant when the momentumstored up in the rapidly rotating armature and shaft apply an abnormallyexcessive torque. With the arrangement shown in the drawings, the effectof this is to tend to screw the pinion still farther to the right but asthe pinion cannot screw farther. toward the right because it is alreadybutting against collar 6, the tendency is to screw the sleeve in theopposite direction thus tending to relieve the frictional pressure ofdisc 9 on annulus 101 This permits the pinion and sleeve to lag behindthe drive shaft during the time needed to take up the shock and startthe fly-wheel of the engine. The pressure of spring 15 being constant,will operate automatically to restore disc-10 to full frictionalengagement with annulus 9 as soon as the abnormal or shock conditionshave been equalized by getting the fly-wheel of the engine in motion andcorresponding slowing down of the motor armature.

It will be understood that the above de scribed endwise movements of thesleeve are likely to be minute and in many cases will manifestthemselves merely as decrease of pressure of the frictional surfacesrather than as observable movements of the sleeve.

It will be evident also that if the pressure of spring 15 be properlygauged so as to afford a closely regulated pressure slightly greaterthan the maximum normal torque, the friction surfaces may slipsuflicient to take up the shock without any endwise movement of thesleeve 3.

In the embodiment of my invention shown in Figure 2, the number andnature of the essential elements is the same but the organization of theparts is different in detail. In this figure, the fly-wheel Gr, pinion4, spring 8, screw sleeve 3 with friction disc 10 may be the same asbefore. The pinion 4, however, when screwed to the end of the sleeve,comes into contact with collar 16 rigidly secured on sleeve 3 by setscrews 4. Hence, screwing the pinion 4 until it butts against the collarcannot have any tendency to screw the sleeve 3 to the left. Anequivalent function is performed in a better and more easilydeterminable manner by the cooperating. friction disc 19 which isinternally screw-threaded as at 1 20 so as to fit the multiple threadsteep pitch screw 21 cut in the outer portion of the armature shaft 2.This friction disc 19 is forced endwise into frictional engagement withdisc 10 by stifiothrust spring 25. This spring like spring 15 previouslydescribed is not a torque spring but operates merely by its endwisethrust to force disc 19 against disc 10 with the pressure required totransmit the normal maximum torque required for starting the engine.

he operation of this form of my invention is similar to that of Figure 1except that in Figure 2, it is the disc 19 that screws rearwardly torelieve the friction pressure at' the inst-ant of maximum shock, thepinion and sleeve being at thisv instant relatively locked by reason ofthe strew forcing pinion 4 into contact with the collar 16 which, asbefore stated, is rigid with the sleeve 3, and thus prohibits furtherrelative movement of sleeve and pinion until the direction of rotarystress is reversed by the starting of the engine and consequent drivingthe pinion at a speed overrunning the speed of the armature shaft.

One functional advantage of the arrangement shown in Figure 2 over thatshown in Figure 1 is that the endwise movement for relieving thepressure and friction of the friction members is predetermined by theing an electric starting motor, a shaft driven thereby, a screw elementrotated by said shaft, a pinion adapted to screw endwise into and out ofengagement with a gear for starting the engine according as said screwelement rotates faster or slower than said pinion, and, in combinationwith said parts,

a friction coupling interposed between the electric starting motor andthe engine, said coupling having frictional engagement suflicient totransmlt the normal power required for driving the-engine up to startingspeed, but insufiicient to withstand the abnormal torque developed bythe momentum of the drivin members acquired during the shifting 0 saidpinion, together with means whereby abnormal torque, applying abnormalendwise screwin efl'ort, operates aut0- matically to reduce t e pressureof the friction elements of said friction coupling.

2. The combination specified by claim 1 in which a. spring. is arrangedas the means to oppose reduction of the pressure of the fricment onthearmature shaft and formed with a friction surface as one element of saidfriction coupling, the cooperatin friction surface being mounted upon anby the armature shaft, said parts being located and relativel arrangedso that the abnormal torque wil cause endwise screwing of one of saidfriction elements in a direction to relieve the surfaces.

4. The combination specified b claim 3, in which asgring is arranged ast e means to oppose uctlon of the pressure of the frictlonal elements. I

5. The combination specified by claim 3, in which the shaft-drivenfrictional element is screw. threaded to the drive shaft, by a screw ofopposite twist to that of the sleeve screw,

.and in which a thrust spring is employed as the means for preventingunscrewing of said shaft engaging friction element under nor-j maltorque but is adapted to yield and permit such movement under abnormaltorque.

Si ed at New York city in the county of New ork, and State of New York,this 13th day of December A. D. 1919. l

- SAMUE W. RUSHMORE.

being driven pressure on their frictional u

